Problem: Divide the following complex numbers: $\dfrac{10(\cos(\frac{17}{12}\pi) + i \sin(\frac{17}{12}\pi))}{2(\cos(\frac{7}{4}\pi) + i \sin(\frac{7}{4}\pi))}$ (The dividend is plotted in blue and the divisor in plotted in green. Your current answer will be plotted orange.) Re Im
Answer: Dividing complex numbers in polar forms can be done by dividing the radii and subtracting the angles. The first number ( $10(\cos(\frac{17}{12}\pi) + i \sin(\frac{17}{12}\pi))$ ) has angle $\frac{17}{12}\pi$ and radius 10. The second number ( $2(\cos(\frac{7}{4}\pi) + i \sin(\frac{7}{4}\pi))$ ) has angle $\frac{7}{4}\pi$ and radius 2. The radius of the result will be $\frac{10}{2}$ , which is 5. The difference of the angles is $\frac{17}{12}\pi - \frac{7}{4}\pi = -\frac{1}{3}\pi$ The angle $-\frac{1}{3}\pi$ is negative. A complex number goes a full circle if its angle is increased by $2 \pi$ , so it goes back to itself. Because of that, angles of complex numbers are convenient to keep between $0$ and $2 \pi$ $-\frac{1}{3}\pi + 2 \pi = \frac{5}{3}\pi$ The radius of the result is $5$ and the angle of the result is $\frac{5}{3}\pi$.